Project Abstract ! Despite decades of intensive research, type 1 diabetes (T1D), which is characterized by autoimmune destruction of the insulin-producing beta cells of the pancreas, still cannot be prevented. Understanding the innate immunologic mechanisms for the development of T1D is crucial for developing preventive strategies. Dissecting the interactions between environmental stimuli such as viral infection, immune responses, and the development of insulitis (a key pathologic feature of T1D) in humans is extremely challenging. By temporally defining such interactions in the rat model of autoimmune diabetes, we believe we can develop specific interventions to target the human disease process. We have found that the type I interferon (IFN) receptor (IFNAR), a key component of the innate immune response to viral infection, is critically involved in development of virus-induced autoimmune diabetes in weanling LEW.1WR1 rats. We will further define the role of type I IFN in the development of diabetes by comparing immune cell recruitment between WT and IFNAR-/- rats and examining transcriptional profiles at the single cell level. We will also determine if intrinsic IFN signaling in islets, including beta cells, contributes to the development of T1D by performing islet transplants between WT and IFNAR-/- rats. Inflammatory pathways also participate in the pathogenesis of autoimmune diabetes. We will determine if blockade of the interleukin-1 (IL-1) receptor will prevent type I IFN-independent diabetes. We will delineate mechanisms by which the anti- inflammatory drug salicylate prevents diabetes. We plan to create a knockout rat using a CRISPR-Cas9 gene editing strategy to examine the inflammatory pathway-mediated contribution to the development of autoimmune diabetes. Through the proposed studies, we will gain a fundamental understanding of immunologic responses that lead to autoimmune diabetes. Notably, we will define both temporal aspects as well as key cell populations involved in innate immune responses. Results from these experiments will reveal specific innate immune pathways that participate in the development of insulitis and autoimmune diabetes and are essential for developing preventive strategies for individuals who are at greatest risk for T1D.